Cancer and other diseases caused by the presence of unwanted cells create significant loss of life, suffering, and economic impact. Immunotherapeutic strategies for targeting cancer have been an active area of translational clinical research.
A variety of other approaches have been explored for immunotherapy, but many of these prior approaches lack sufficient specificity to particular unwanted cells. For example, demibodies have been designed each having an scFv portion binding to different antigens on a target cell, an Fc domain allowing pairing to a complementary demibody, and a binding partner capable of forming an association to another binding partner on a complementary demibody. WO 2007/062466. These demibodies, however, are not necessarily specific to cancer cells and could bind and have activity on other cells expressing the same antigens. See also WO 2013/104804, which provides a first polypeptide with a targeting moiety binding to a first antigen and a first fragment of a functional domain, along with a second polypeptide with a targeting moiety binding to a second antigen and a second fragment of a functional domain that is complementary to the first fragment of the functional domain. Likewise, this approach is not necessarily specific to cancer cells and could bind and have activity on other cells expressing the same antigens.
While some positive test data has been shown with prior approaches, clinically-effective therapeutic strategies must be able to elicit a strong immune response in an individual suffering from a disease such as cancer. Additionally, effective therapies should be very specific and not cause unwanted side effects to other cell types in the body. Therefore, additional developments in this field of re-directed immunotherapy are required.